Arrangement for controlling cooling in continuous casting of metals



Jan. 16, 1968 A. .1. WERTLI ARRANGEMENT FOR CONTROLLING OL IN CONTINUOUS CASTING OF TAL Filed April 6, 1967 2 Sheets-Sheet 1 Jan. 16, 1968 A. .1. WERTLI ARRANGEMENT FOR CONTROLLING COOLING IN CONTINUOUS CASTING OF METALS 2 Sheets-Sheet Filed April 6, 1967 United States Patent 7 Claims (31. '164--273) ABSTRACT OF THE DISCLOSURE A heat-damn1ing layer is disposed between a mold for a continuous metal casting and the cooling chamber surrounding the mold. The damming layer dams the heat transmission from the mold to the cooling chamber in order to control the cooling of the metal melt. This allows the melt to be brought into the mold directly while hot.

This application is a continuation-in-part of my copending application Ser. No. 376,359, filed June 19, 1964, now abandoned.

The invention relates to an arrangement for continuously casting metals, particularly ferroalloys, the arrangement including at least one mold and cooling means surrounding the mold.

In conventional arrangements of this type a large portion of the length of the mold is closely surrounded by the cooling means. Because of the good heat conductivity of the mold which usually is made of graphite, it may happen that at the inlet of the mold so much heat is released from the metallic melt that the melt solidifies already close to the inlet of the mold and after a relatively short time clogs the inlet opening. This happens particularly quickly if metal rods of small diameter are cast. The heat abduction through the mold also influences the speed of solidifying of the metal melt in the mold which influences the texture of the metal rod. When casting thin metal rods of grey iron undesired white solidification may occur because of too quick solidification, i.e. iron carbide forms during cooling. Improving the cooling process by increasing the thickness of the wall of the mold entails such great wall thickness that continuous casting becomes uneconomical, considering the' high cost of graphite, and does not avoid solidification of the melt before entering the mold due to heat abduction.

In the arrangement according to the invention a layer damming heat transmission from the mold to the cooling means is provided between the mold and the cooling means. By the provision of this heat-damming layer the cooling process can be favorably influenced in a simple manner while, at the same time, the amount of the material of which the mold is made, which is usually graphite, is reduced. With the new arrangement the cost of the mold is low. The favorable influence on the cooling process is particularly apparent when casting thin rods of grey iron, because, by suitable selection of the material and thickness of the heat-damming layer, the speed of solidification can be controlled between the optimal possible upper limit for continuous casting and the conventional lower limit for sand casting. When casting thin, grey iron rods a grey solidified texture can be obtained throughout the entire cross section; the undesired white solidification is avoided.

In an advantageous embodiment of the invention the layer made of heat-damming material is arranged in the form of a sleeve between the mold and the cooling means whereby, if desired, an air space may be provided between ICC the cooling means and the sleeve for additionally affecting the cooling process.

The arrangement according to the invention is not limited to the provision of one mold within the cooling means, but is also applicable to arrangements for simultaneous casting of a plurality of rods.

The novel features which are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, and additional objects and advantages thereof will best be understood from the following descripition of embodiments thereof when read in connection with the accompanying drawing wherein:

FIG. 1 is a longitudinal section through a mold according to the invention, the section being made along line C-D of FIG. 2.

FIG. 2 is a cross section of the arrangement shown in FIG. 1, the section being made along line A-B of FIG. 1.

FIG. 3 is a longitudinal part-sectional view of a modified mold according to the invention.

FIG. 4 is a cross-sectional illustration of an arrangement according to the invention having three molds.

FIG. 5 is a cross-sectional illustration of an arrangement according to the invention having four molds.

FIG. 6 is a cross-sectional illustration of an arrangement of three rod forming channels in a single mold.

FIG. 7 is a cross-sectional illustration of the mold of FIG. 1 connected to a horizontal continuous casting furnace.

In the arrangements shown in FIGS. 1 and 2 a layer damming heat transmission from a open ended mold to cooling means is provided in the form of a sleeve 2 made of heat-damming material and placed betweenamold 1 and cooling means 3. The mold 1 is made, for example, of graphite and a metal rod having a circular cross section in this particular case is formed from a liquid metal melt. Instead of graphite other materials may be used if they have also a good heat conductivity, non-wetability by the melt, and good lubricating qualities, i.e. little friction between the between the metal rod and the mold. The material of which the sleeve 2 is made has a lower coefficient of heat conductivity 7\ than the material of which the mold is made. The sleeve 2 may be made of ceramic or of metal, for example, steel, grey iron, or the like. Referring to FIG. 7, the left end 5 of the mold 1 is inserted into the lower end of a horizontal-type continuous casting thermostatic furnace 34 to communicate with the hot melt 23 therein. The end 5 of the mold 1 is held within a holder 24 inside the furnace 34. The holder 24 which is made of ceramic material of very low heat conductive properties, such as silimanite, is fixed within the ramming 25 and wall 26 of heat insulating bricks inside the furnace 34. In addition to being held within holder 24, the mold 1 passes through a surrounding insulation block 30 of heat-damming material fixed within a suitable aperture in the steel sheet 27 of the furnace 34. The block 30 is formed, as with a flange, so as to be positioned between the cooling means 3 and furnace 34 in order to prevent a heat transfer from the mold 1 to the surrounding structure. The cooling means 3 which is cylindrical in shape has a water inlet 31 which permits passage of cooling water into a water guiding spiral passage 33 within the cooling means 3 and a water outlet 32 which permits passage of water out of the passage 33. The right end of the mold 1 abuts against a shoulder 6 in the sleeve 2. The sleeve 2 is slightly conical and the bore of the surrounding cooling means is correspondingly slightly conical so that, when casting, whereby the cooling means according to FIG. 1 are pressed to the left,

the end 5 of the mold is pressed firmly into the outlet of 3 the furnace 34. An annular recess 4 is provided in the outside of the sleeve 2 at the entire circumference thereof. This recess forms with the wall of the bore in the cooling means 3 an air space or gap which acts as an additional heat-damming layer.

When casting, liquid metal from melt 23 enters the mold at the left end 5, cools and leaves the mold at the opposite end as a solidified rod 28. In passing through the mold 1, the melt flows through a zone, for example, of 3 to 6 inches, which is well insulated to the outside by insulation block 30 so as to prevent the melt from becoming undercooled within this zone in the mold 1. Thereafter, the melt begins to solidify in a zone 29 approximately coincident with the left end of the cooling means 3. The point at which the zone 29 of solidification begins is determined by the heat damming sleeve 2. The sleeve 2 also controls the continued process of solidification. Thus, the invention makes it possible to bring melt 23 into the solidification zone 29 while very hot and only thereafter to cool the melt in a controlled manner. Alternatively, the sleeve 2 can be omitted in favor of an air gap which provides the same functions as the sleeve 2. Upon leaving the mold 1, the solid rod 28 is gripped by a pulling mechanism, now shown, and preferably intermittently pulled away.

By inserting the sleeve 2 made of heat-damming material a premature solidification of the melt in the vicinity of the end 5 of the mold is prevented. Aside from this, such cooling velocity of the metal in the mold 1 is obtained that the texture of the finished rod is homogeneous and of a good quality. If, for example, a strip is cast of grey iron, the strip should have a grey solidified texture throughout its entire cross section, i.e. when cooling the melt, the carbon contained in the melt should be equally distributed and should be separated as fine graphite. This is achieved by maintaining the cooling velocity sufficiently great by suitable choice of the material and of the dimensions of the sleeve 2. By the arrangement according to the invention White solidification of the grey iron is prevented, i.e. the carbon in the melt is not separated together with iron as iron carbide. The cooling velocity is of importance also when casting metals other than grey iron and the arrangement according to the invention is also suitable for continuous casting of steel and nonferrous metals.

In the embodiment of the invention shown in FIG. 3, in addition to the recess 4 which is shorter than in the arrangement shown in FIG. 1, a recess 7 is provided which extends from the left end of the sleeve 2 between the sleeve and the cooling means 3. Between the recesses 4 and 7 an annular collar 8 is retained for better support of the sleeve 2 in the cooling means 3. The additional recess 7 forms an air space which dams the heat flow from the mold end 5 extending into the outlet opening of the furnace, not shown, to the cooling means 3 so that a premature solidification of the melt at the inlet of the mold is particularly eifectively avoided. In all other respects the arrangement shown in FIG. 3 corresponds to that shown in FIGS. 1, 2 and 7.

In the embodiment shown in FIG. 4 one cooling means 3 serves three molds 1 which are arranged on a circle in a block 9 made of heat-damming material. The molds 1 are closely adjacent to the surrounding walls of respective bores in the block 9 which may be eifected by inserting the molds at a temperature which is lower than that of the block 9 in whose bores the molds are inserted whereafter the diameter of the mold increases due to heat expansion and the molds are firmly pressed onto the walls formed by the bores. In the center of the circle on which the molds are placed an additional cooling means 10 is provided which essentially consists of a tube 12 extending through a bore 11 in the block element 9. The bore 11 is closed at the end facing the furnace. At the other end of the bore 11 the tube 12 projects from the block 9. At this end the bore 11 is provided with a water inlet and the projecting end of the tube 12 is provided with a water outlet so that cooling water flows through the annular space between the bore 11 and the tube 12 into the cooling means and leaves the cooling means through the tube 12. Due to the provision of the additional cooling device 10 the molds 1 are substantially equally cooled at all sides which advantageously affects the solidification velocity and therefore also the texture of the metal rods in the molds. In the embodiment of the invention shown in FIG. 4, air spaces 4 are provided between the cooling means 3 and the block 9 which spaces are formed by recesses in the circumference of the block 9. The recesses do not extend around the entire circumference of the block 9 but only in the neighborhood of the molds 1. Protuberances 13 are provided separating the air spaces 4.

In the embodiment of the invention shown in FIG. 5, four molds 1 are provided in one cooling means 3. They are arranged on a circle in a block of heat-damming material. This block is subdivided into three segments 14, 15 and 16 in the direction of the axes of the molds. The four molds 1 are arranged in pairs between the segments 14, 15 and 15, 16. Spaces are provided between the segments which act as heat-damming air spaces 17, 18. The three segments are connected by counter-sunk bolts, not shown. In the center of the circle on which the four molds are placed an additional cooling means is provided in the same manner as in the arrangement shown in FIG. 4. If desired, in the arrangement shown in FIG. 5 recesses similar to those shown in FIG. 4 may be provided in the segments in order to form air spaces or gaps between the segments and the cooling means 3 in the neighborhood of the molds.

In the embodiment of the invention shown in FIG. 6 one mold 1 is associated with cooling means 3, the mold being provided with three channels 19 arranged on a circle. When casting, a metal rod forms in each of the channels 19. A sleeve 2 made of heat-damming material is provided between the mold 1 and the cooling means 3. Cooling means 10' are located in the interior of the mold 1 which cooling means comprise concentric tubes 21 and 22. The outer tube 21 is in intimate contact with the wall of a bore in the center of the mold. The end of this central bore facing the furnace is closed; also closed is the corresponding end of the outer tube 21. The corresponding end of the inner tube 22, however, is open so that a coolant can be admitted through the interior tube 22 and removed through the annular space between the inner tube 22 and the outer tube 21. In the embodiment shown in FIG. 6, heat-damming air spaces or gaps may be provided between the sleeve 2 and the cooling means 3 similar to the air spaces of the arrangement shown in FIG. 4.

The invention is not limited to arrangements for horizontal continuous casting, but may also be used for vertical continuous casting.

What is claimed is:

1. In combination with a furnace for continuous casting of metal: I

at least one open ended mold projecting from said furnace and having a longitudinal bore communicating with the interior of said furnace for passage of liquid metal from said furnace thereinto;

a cooling means surrounding said mold outside of said furnace for cooling of the liquid metal in said mold to a solidified rod, and

a heat-damming layer interposed between said mold and said cooling means for damming heat transmission from said mold to said cooling means.

2. A combination as defined in claim 1 wherein said layer is a sleeve.

3. A combination as defined in claim 2 wherein said sleeve is made of a metal whose coefiicient of thermal conductivity is smaller than that of the material of which said mold is made.

4. A combination as defined in claim 2 comprising an air gap arranged between said cooling means and said sleeve and being coextensive with at least a portion of said cooling means for additionally damming heat transmission from said mold to said cooling means.

5. A combination as defined in claim 4 wherein said air gap is formed on the outside of said sleeve.

6. A combination as defined in claim 1 wherein said layer is a block element and wherein a plurality of molds are disposed in said block element, each said mold having a longitudinal bore communicating with the interior of said furnace for passage of liquid metal thereinto whereby said cooling means cools the liquid metal in each said mold to a solidified rod.

7. A combination as defined in claim 6 wherein said molds are placed on a circle, and an additional cooling means is placed in said block element in the center of the circle on which said molds are placed.

8. A combination as defined in claim 6 wherein said block element is divided to form a plurality of block segments, said molds being placed between said segments in spaced relation to form air gaps between said segments for additionally damming heat transmission from said molds to said cooling means.

9. A combination as defined in claim 1 wherein said mold includes a plurality of parallel channels therein for receiving liquid metal from said furnace and conducting the metal in a plurality of rods through said mold while the metal is solidified by cooling.

10. A combination as defined in claim 1 having an insulation block of heat damming material disposed between said furnace and said mold and cooling means.

References Cited UNITED STATES PATENTS 657,610 9/1900 Mitchell 249-79 XR 967,830 8/1910 P otter 164-122 1,828,335 10/1931 Millspaugh 164-122 XR 1,988,258 4/1935 Snook 164-123 XR 2,281,718 5/1942 Scully et a1. 164-l23 2,672,665 3/1954 Gardner et al. 164-283 XR FOREIGN PATENTS 497,043 8/ 1964 Italy.

I. SPENCER OVERHOLSER, Primary Examiner. R. ANNEAR, Assistant Examiner. 

